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Physiology > Respiratory System 3 > Flashcards

Respiratory System 3 Flashcards

1
Q

Describe Pulmonary circulation

A
  • Lungs receive 100% of cardiac output
  • Pulmonary vs bronchial artery
  • Pulmonary artery brings oxygen depleted blood from the right heart to the lungs
  • Pulmonary capillaries cover the alveoli like a sheet
  • Oxygen enriched blood then leaves the lung via the pulmonary veins
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2
Q

Contrast mean arterial pressure of pulmonary and systemic circulation

A

Pulmonary circulation- 10-17mm Hg

Systemic circulation- 95 mm Hg

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3
Q

Contrast resistance in pulmonary circulation and systemic circulation

A

Pulmonary circulation - low(2-3 mm Hg/L/min)

Systemic circulation- high

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4
Q

Contrast the compliance pulmonary circulation and systemic circulation

A

Pulmonary- High ( less smooth muscle in arteriolear wall)

Systemic- low

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5
Q

Contrast response to hypoxia in pulmonary and systemic circulation

A

Pulmonary- vasoconstriction (PAO2 sensitivity)

Systemic- vasodilation

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6
Q

What is the formula for resistance?

A

Resistance= pressure gradient/ flow

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7
Q

What is the normal flow?

A

Flow/cardiac output= 5 L/min or 83 ml/s

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8
Q

What is the systemic resistance?

A

93 mm Hg/ 83 ml/s= 1.1 peripheral resistance unit

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9
Q

What is the pulmonary resistance?

A

7 mm Hg/ 83 ml/s= 0.08 peripheral resistance unit

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10
Q

What are the main differences between pulmonary and systemic circulation?

A
  • Pulmonary circulation pumps blood to the top of the lung, systemic circulation pumps pumps blood to the entire body even ab9ve the head height
  • Little smooth muscle in arteries and arterioles making it very compliant, thick arteries and arterioles allows for maximum diversion of blood to major organs
  • Thin pulmonary capillary walls could leak blood into lungs (pulmonary edema) under high pressure
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11
Q

An increase in cardiac output results in decreased pulmonary vascular resistance. Why is this beneficial?

A
  1. Increased capillary surface area, which enhances gas exchange
  2. Protective against high capillary pressures that can cause pulmonary edema
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12
Q

Explain the relationship between cardiac output and vascular resistance

A

At rest capillary beds at the apex are closed because of low hydrostatic pressure

  • The base of the lung has higher blood flow (perfusion) because of gravity
  • Increased cardiac output results in increased pulmonary arterial pressure
  • This increase in pressure causes the apical capillaries to open (recruitment)
  • Increased surface area resulting in more perfusion and gas exchange
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13
Q

As pulmonary arterial pressure increases the pulmonary vascular resistance falls because of…

A
  1. Recruitment:
    • Principal mechanism for fall in pulmonary vascular resistance
  2. Distention:
    • Widening of capillary segments due to high compliance of pulmonary vessels

With recruitment and distention of capillaries there is increased surface area resulting in more blood flow(perfusion)

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14
Q

Explain the hypoxia vascular response

A

Hypoxia stimulates vasoconstriction in the pulmonary vessels (the exact mechanism is unknown)

Hypoxia- induced pulmonary vasoconstriction is accentuated by high carbon dioxide and low blood pH

There can be regional alveolar hypoxia or generalized alveolar hypoxia

With alveolar hypoxia there is a low ventilation/perfusion (Va/Q) ratio

Once the hypoxia has been resolved the vessels dilate and blood flow is restored

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15
Q

At lower oxygen tensions ( decreased PO2) the pulmonary vessels constrict to allow…

A

Blood to be direct t better ventilated areas. As oxygen tensions increase this changes

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16
Q

What is a pulmonary edema?

A

Abnormal accumulation of fluid in lung interstitium and alveoli

  • Edema results from either decreased oncotic pressure or increased hydrostatic pressure(starling forces)
  • In the lung the alveolar surface tension augments filtration and alveolar pressure opposes filtration

Normal conditions:

  • Net secretion of fluid into interstitium
  • Drained by lymphatic
17
Q

What type of disease is pulmonary edema?

A

Pulmonary edema is classified as cardiogenic or noncardiogenic

  • Cardiogenic pulmonary edema is due to increased pulmonary capillary hydrostatic pressure
  • Noncardiogenic pulmonary edema arises due to direct or indirect insult to the membrane permeability of the pulmonary capillary
  • It results in decreased surface area for gas exchange and increased; the diffusion SL distance is also increased
18
Q

What causes inflammation?

A

Etiology- irritants, positive pressure ventilation

Capillary permeability

19
Q

What is the etiology of IRDS?

A

Increased surface tension

20
Q

What is the etiology of Tumor obstructing lymphatics?

A

Etiology- reduced lymphatic drainage

21
Q

What is the etiology of overtransfusion?

A

Etiology- reduced oncotic pressure

22
Q

What are the factors that affect diffusion?

A

Gas uptake is determined by three factors:

  1. Diffusional properties of the alveolar-capillary membrane
  2. The partial pressure gradient of the respiratory gases
  3. Pulmonary capillary blood flow
23
Q

How much alveoli in an adult?

A

300 to 500 million alveoli in adult lung

24
Q

What is the surface area of the alveoli in an adult?

A

75 m^2

25
Q

Why do we need large surface area?

A

Large sheet of blood vessels

Approximately 60,000 terminal respiratory units (alveoli merge with pulmonary capillaries)

26
Q

What are the diffusion barriers?

A
  1. Alveolar liquid
  2. Apical membrane of type 1 cell
  3. Cross the cytoplasm
  4. Basolateral membrane of type 1 cell
  5. Extracellular space
  6. Endothelial cell membrane
  7. Plasma
  8. RBC membrane
  9. RBC cytoplasm
  10. Hemoglobin
27
Q

What is the partial pressure gradient ?

A

The partial pressure gradient facilitates gas exchange

-Consider the partial pressure of oxygen and carbon dioxide in the alveoli as compared to the pulmonary artery

28
Q

How does high altitude effect the volume of gas exchanged per unit time?

A

With increasing altitude there is lower barometric pressure—> lower PaO2–> lower driving pressure—> decreased volume of gas exchanged per unit time

29
Q

What is the capillary reserve time?

A

Blood transit time in the alveolar capillary is 0.75s

PO2 equilibriates within the first 0.25 s

Reserve time= 0.75s-0.25= 0.5s

-With increased cardiac output there is reduced transit time which facilitates more gas exchange

30
Q

A diffusional impairment will shorten reserve time as seen in:

A
  • pulmonary fibrosis
  • pulmonary edema

Capillary and alveolar PO2 will not equilibrate

Physiology (36 decks)

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